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Simon Yam as Chang Chia-chun (張家俊), a landlord who likes spying his tenants. Chang was an undercover police officer who entered an asylum to arrest serial killer Huang Si-lang but was tortured as his superior officer became a vegetable, unable to prove his identity as a police officer. Chang was released from the asylum after his wife found his diary, but his personality have become twisted and seeks revenge on those who have abused him. •
Lee Kang-sheng as Kuo Li (郭力), a homosexual tenant as described by Chang, while in actuality, Kuo is cancer sufferer. •
Kaiser Chuang as Chang Kuo-sheng (張國生), a tenant who is a lusty gymnastics teacher with a criminal record of domestic violence and enjoys spying on others and drinking expired milk as described by Chang, while in actuality, Chang is a college professor who is homosexual. •
Ivy Shao as Chang Ying-ru (張穎如), Chang's daughter who was murdered by serial killer Huang Si-lang. The Ying-ru in the story as Chang described to the police interrogator is actually himself. • Sophia Li as Chen Min-hui (陳敏慧), one of the tenants who is an office lady often engaging in infidelity as described by Chang, while in actuality, Chen is the wife of Wang Ming-kai and mother of Wang Yun-ko. • Yu An-shun as Wang Ming-kai (王名凱), a divorced tenants who has sexual fantasies about his daughter as described by Chang, while in actuality, Wang is married to Chen Min-hui and the father of Wang Yun-ko in a happy family of three. • Hou Yan-xi as Bo-yan (柏彥), one of the tenants who is a useless college student who believes the existence of teleportation when Chang puts him unconscious with sleeping pills and moves him to a different location as described by Chang. In actuality, Bo-yan is a hard-working medical student who is also homosexual. • Bernard Sen as Ling Hu (令狐), a homosexual tenant who is Kuo Li's boyfriend as described by Chang, while in actuality, Ling is Kuo's nephew who would occasionally visit his uncle and take care of him. •
Angel Ho as Wang Yun-ko (王芸可), one of the tenants who is Wang Ming-kai's daughter as described by Chang, while in actuality, Wang is indeed Wang Min-kai's daughter but is also Chen Min-hui's daughter. •
Akio Chen as Huang Si-lang (黃四郎), the previous owner of the apartment as described by Chang, while in actuality, Huang is a serial killer who Chang was determined to arrest in the past. Huang rescued Chang from the asylum and hanged himself afterwards. • Feng Kai as a police officer who interrogates the landlord. • Kurt Chou as a doctor in the asylum who once raped Chang Chia-chun. He was later tortured to death by Chang and became his first victim. • Kitamura Toyoharu as Min-hui's superior who has a relationship with her. • Alex Ko as a police officer. • Don Wong as Officer Chen (陳警官) • Chang Chiong-chi as Officer Chen's wife. •
Shen Meng-sheng as an old man. • Ryan Kuo as a police officer. • Tu Shih-mei as an asylum staff who forced Chang to eat. She was later abducted by Chang to the apartment where he forced her to drink detergent the same way she forced him to eat and dies as a result, becoming Chang's second victim. ==Production==